崇明东滩表层沉积物中~7Be活度的粒度效应

The grain size effect of ~7Be activity in surface sediments of Chongming tidal flat,China

本文于2010年7月至2011年2月期间,每月于长江口区域崇明东滩的高、中、低不同潮滩采集表层沉积物样品,利用水淘选原理和沉积物分级装置进行粒度分级,获得从粗到细的A、B、C、D四种不同粒径大小(>63μm、32~63μm、16~32μm以及8~16μm)的样品组分及其相应的7Be活度。研究结果表明:粗粒级部分的含量随着离岸距离的增加而增高;细粒部分则反之。粒度由细到粗,7Be活度呈降低趋势。对分级后样品的粒径(Φ单位)与7Be活度值做相关性研究发现,高、中潮滩沉积物7Be核素活度受降水影响大于低潮滩沉积物。相较于中低潮滩,位于高潮滩的14#站位,7Be活度与平均粒径的相关性最差。7Be活度和平均粒径相关性的季节性差异不甚明显。本研究结果表明,在利用7Be研究河口海岸区域中季节时间尺度颗粒悬浮物的输运和沉积过程当中,应充分考虑粒度效应的影响。

The time-series surface sediments were collected monthly in high flat phragmites australis zone,middle flat scirpus triqueter zone and low flat zone,respectively,at Chongming tidal flat which lies in Changjiang Estuary during July 2010 and February 2011.By using a water elutriation apparatus,sediments were separated into four size fractions from 8~16 μm to >63 μm which were called A(the coarsest),B,C and D(the finest).In order to know the distribution of 7Be in different size fractions and different seasons,sediment grain size was measured as well as 7Be activity.The following conclusions were drawn:In the same level the coarse-particle fraction exhibited an offshore increasing trend,and the fine fraction showed a decreasing trend.The activities of 7Be generally decreased as the grain size increased.Correlation analysis between grain size and 7Be activity showed that the 7Be activity of sediment in high and middle tidal flat were influenced by the precipitation more than that of the low tidal flat.The correlation between grain size and 7Be activity at station 14# was weakest among all the sampling stations.However,there was no obvious seasonal difference for the correlation between grain size and 7Be activity.Our study showed that the grain size effect of 7Be activity should be considered when 7Be is utilized to trace transport and deposition of particles in the estuary and coastal areas on a seasonal scale.